Are you poisoning your family with fish?

A bite-by-bite analysis of the fish on your plate.

Are you poisoning your family with fish? That's the essence of the question that one San Franciscan man recently took it upon himself to answer. David Ewing Duncan, author of the newly released book, "Experimental Man," put science to the test to find out just how much mercury and other toxins he was ingesting with each bite of fish. His results were unsettling.

The Environmental Protection Agency (EPA) insists that "most people's fish consumption does not cause a health concern." Still, the agency concedes that high levels of mercury in the bloodstream of unborn babies and young children may harm the developing nervous system. The agency advises women who are pregnant, nursing, or of childbearing age, and young children to limit their consumption of certain types of fish and avoid eating shark, swordfish, king mackerel, or tilefish altogether because they contain high levels of mercury.

The EPA's blood threshold for methylmercury, the most common form of mercury that accumulates in the body, is 5.8 µg/l (micrograms per liter.) To test his own levels of methylmercury, Duncan submitted blood and urine tests for lab analysis both before and after eating fish. In the "before" tests, Duncan registered a level of less than 4 µg/l, well within safe limits. A few days later, after eating halibut for lunch and swordfish for dinner, Duncan again submitted blood and urine tests for methylmercury analysis. This time, the lab work showed that his methylmercury level had spiked to 13 µg/l, well ABOVE the EPA's safe threshold. And considering that children have suffered losses in IQ at levels just slightly above 5.8 µg/l, the results are nothing if not unsettling.

Time and time again, consumers are told that fish is a safe, healthy source of lean protein and fatty acids, but do the health benefits outweigh the toxin risk? One thing is certain, if you do choose to eat fish, choose those varieties that contain the least amount of mercury and limit your consumption to just a few servings a week.